This invention relates to a compound-semiconductor single-crystal manufacturing apparatus which progressively pulls up a compound-semiconductor single crystal by the liquid encapsulated Czochralski (LEC) process.
Recently, the LEC process has been applied in the manufacture of a compound-semiconductor single crystal having a high decomposition pressure at the melting point such as GaAs, GaP InP. However, this LEC process has the drawback that since a crystal is grown at high temperature and under high pressure and a rigid heating condition for the growth of a crystal, difficulty is encountered in the stable production of a single crystal or in controlling the quality of a crystal produced.
In the LEC process, a crucible is supported in a pressure vessel by the aid of a crucible holder. The crucible is heated by a heating element concentrically surrounding the crucible. As a result, the crucible is filled with a molten raw material and a liquid capsule layer covering said raw material. The high temperature decomposition of said molten raw material is obstructed by said liquid capsule layer and pressurized inert gas. A single crystal is manufactured by being rotatingly pulled up through said liquid capsule layer. In this case, various heat shields are set up on the outside, top and bottom sides of the heat element in order to ensure the heating efficiency of the heat element and a proper temperature distribution within the crucible. These heat shields and the crucible are generally prepared from carbon material.
However, the carbon material is readily oxidized by minute amounts of, for example, oxygen and steam in the atmosphere, and deteriorated in quality. Therefore, difficulties are experienced in maintaining the efficiency of heating the crucible by the heat element and the proper temperature distribution within the crucible. Further, the molten raw material is contaminated by the growth of carbon oxides. The above-mentioned circumstances have presented considerable difficulties in maintaining a high yield of a compound-semiconductor single crystal and in maintaining its quality.